Diesel power piston surface ceramic coating material, thermal barrier coating and preparation method thereof

Abstract

The invention provides a diesel power piston surface ceramic coating material, a thermal barrier coating and a preparation method thereof, and relates to the field of ceramic coatings. The ceramic coating material is uniformly mixed plasma spraying composite powder and comprises 8YSZ powder, cordierite powder and silicon oxide powder, and the hollow rate of the 8YSZ powder is 30-45%; the particle size of the cordierite powder is not greater than 30 [mu] m, the content of the cordierite powder is 20-30 wt.%, the content of the silicon oxide powder is 5-8 wt.%, and the balance is the 8YSZ powder. According to the ceramic coating obtained by spraying the ceramic coating material through an atmospheric plasma spraying process, cordierite with a porous and multiphase structure and relatively low density and volume heat capacity is uniformly doped in the ceramic coating, and pores are distributed at intervals, so that the whole ceramic coating has low volume heat capacity and low heat conductivity; and the ceramic coating is also relatively high in bonding strength and relatively low in density, so that the thermal efficiency of diesel power can be improved, and the oil consumption of an engine is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic coating, in particular to a diesel power piston surface ceramic coating material, a thermal barrier coating and a preparation method thereof. BACKGROUND

[0002] Since the 1970s, when Cummins proposed the concept of adiabatic engine, a research and verification boom has been rapidly launched worldwide. The main idea is to use ceramic parts or metal-ceramic composite parts, such as cylinder sleeves and pistons, to reduce heat dissipation, improve engine adiabatic effect, improve fuel efficiency and reduce harmful combustion products and gas emissions. Due to the high performance dispersion and poor economy of ceramic materials, foreign countries have carried out systematic ceramic coating research, including zirconia, mullite, chromium oxide and other ceramic coatings, and the mainstream process is plasma spraying. After more than ten years of technical verification and actual road test verification, it is found that the differences in combustion and emission data are large, so it has not been applied in large quantities in commercial power, and only in high-performance power, such as F1 racing power.

[0003] In recent years, aluminum alloy piston surface PEO (Plasma Electrolytic Oxidation) conversion film has appeared, which has been applied in commercial diesel power and significantly improved the thermal efficiency. This kind of coating with the characteristic of coating temperature fluctuating with the combustion chamber environment temperature is called "thermal swing" coating. Due to the advantages of low density, low thermal conductivity and low volumetric heat capacity, it can significantly improve the thermal efficiency of the engine and is widely concerned.

[0004] In the diesel power development roadmap, thermal barrier coating is still the focus of diesel power manufacturers such as Cummins, MTU and Volvo. They are still carrying out matching, durability design and research to improve the thermal efficiency of adiabatic engines and reduce emissions, which is still one of the important directions. Combined with the technical development of thermal swing coating, the preparation of low-density, low-volumetric heat capacity and low-thermal conductivity coating has become an important development trend. The volumetric heat capacity of traditional 8YSZ thermal barrier coating is relatively large, between 3000-5000 KJ / m 3 Even through atmospheric plasma spraying, due to its large density and specific heat capacity, the reduction of volumetric heat capacity is very limited, which cannot meet the needs of improving the thermal efficiency and reducing fuel consumption of diesel engines. SUMMARY

[0005] The first object of the present application is to provide a diesel power piston surface ceramic coating material to solve the technical problem of low thermal efficiency of diesel engines caused by the relatively large volumetric heat capacity of traditional 8YSZ thermal barrier coating.

[0006] The diesel-powered piston surface ceramic coating material provided by the application is a composite powder, wherein the 8YSZ powder has high fracture toughness, and the high hollow rate of 30-45% enables the 8YSZ powder to form a well-bonded framework in the plasma spraying and melting deposition process, thereby improving the overall bonding force of the ceramic coating; the mineral raw material cordierite has the characteristics of low density, low specific heat capacity, low melting point, low thermal expansion coefficient and the like, and has a high content, plays a role of partially melting deposition and partially semi-melting into the coating interior, and can reduce the density and volume heat capacity of each part as a whole; the melting point of the silicon oxide is low, and the molten silicon oxide can play a role of enhancing the layer bonding force of the atmospheric plasma spraying, and at the same time, the silicon oxide also has the characteristic of low density, and can reduce the overall density. After the 8YSZ powder, the cordierite powder and the silicon oxide powder are uniformly mixed at an optimized ratio, the ceramic coating material provided by the application is obtained.

[0007] Further, in the 8YSZ powder, the impurity content of a single oxide is less than 100 ppm, and the hafnium oxide content is less than 2 wt.%.

[0008] Further, the particle size of the 8YSZ powder ranges from 25 to 75 μm.

[0009] Further, the 8YSZ powder is a spherical powder prepared by an agglomeration sintering-plasma spheroidization process.

[0010] Further, the cordierite powder is an irregularly shaped powder prepared by a crushing method.

[0011] Further, the purity of the silicon oxide powder is greater than 99.5 wt.%.

[0012] Further, the ceramic coating material is a composite powder uniformly mixed by a mechanical method.

[0013] The diesel-powered piston surface ceramic coating material provided by the application has the following beneficial effects:

[0014] The diesel-powered piston surface ceramic coating material provided by the application is a composite powder, wherein the 8YSZ powder has high fracture toughness, and the high hollow rate of 30-45% enables the 8YSZ powder to form a well-bonded framework in the plasma spraying and melting deposition process, thereby improving the overall bonding force of the ceramic coating; the mineral raw material cordierite has the characteristics of low density, low specific heat capacity, low melting point, low thermal expansion coefficient and the like, and has a high content, plays a role of partially melting deposition and partially semi-melting into the coating interior, and can reduce the density and volume heat capacity of each part as a whole; the melting point of the silicon oxide is low, and the molten silicon oxide can play a role of enhancing the layer bonding force of the atmospheric plasma spraying, and at the same time, the silicon oxide also has the characteristic of low density, and can reduce the overall density. After the 8YSZ powder, the cordierite powder and the silicon oxide powder are uniformly mixed at an optimized ratio, the ceramic coating material provided by the application is obtained.

[0015] The ceramic coating material is used to obtain a ceramic coating by atmospheric plasma spraying process, the ceramic coating has a porous and complex phase structure, a lower density and a lower specific heat capacity of the cordierite uniformly doped in the inside, and a pore interval distribution, so that the whole ceramic coating has a low volume heat capacity and a low thermal conductivity, and the thermal conductivity is less than 0.6 W / m·K and the volume heat capacity is less than 2000 KJ / m 3 K. Due to the effects of 8YSZ and silicon oxide, the bonding strength of the ceramic coating is also relatively high, which can be greater than 30 MPa, so that the anti-peeling ability is strong. In addition, due to the high hollow rate of 8YSZ and the low density of cordierite and silicon oxide, the density of the above ceramic coating is also relatively low. That is, the ceramic coating prepared by the diesel power piston surface ceramic coating material provided by the present application has the advantages of low volume heat capacity, low thermal conductivity, low density and high bonding strength, can meet the application requirements of the high-performance coating of the diesel power piston surface, can improve the diesel power thermal efficiency, reduce the engine oil consumption, and has excellent service reliability.

[0016] The second object of the present application is to provide a diesel power piston surface thermal barrier coating preparation method to solve the technical problem that the volume heat capacity of the traditional 8YSZ thermal barrier coating is relatively large, resulting in a relatively low diesel engine thermal efficiency.

[0017] The diesel power piston surface thermal barrier coating preparation method provided by the present application comprises the following steps:

[0018] Preparation of the adhesive layer: an MCrAlY metal adhesive layer is prepared on the surface of the diesel power piston by using a supersonic flame spraying process or an atmospheric plasma spraying process, and the thickness of the adhesive layer is in the range of 50-150 μm;

[0019] Preparation of the ceramic coating: the ceramic coating material is used for atmospheric plasma spraying on the adhesive layer, the flow rate of the primary gas argon is in the range of 27-33 slpm, the flow rate of the secondary gas hydrogen is in the range of 5-10 slpm, the spraying power of the spraying gun is in the range of 30-42 kW, the spraying distance is in the range of 80-100 mm, and the powder feeding amount is in the range of 20-40 g / min.

[0020] The diesel power piston surface thermal barrier coating preparation method provided by the present application has all the advantages of the ceramic coating material, which will not be described here.

[0021] The third object of the present application is to provide a diesel power piston surface thermal barrier coating to solve the technical problem that the volume heat capacity of the traditional 8YSZ thermal barrier coating is relatively large, resulting in a relatively low diesel engine thermal efficiency.

[0022] The diesel-powered piston surface thermal barrier coating provided by the present application is prepared by using the ceramic coating material and the preparation method described above.

[0023] Further, the thickness of the ceramic coating ranges from 200 to 500 μm.

[0024] The diesel-powered piston surface thermal barrier coating provided by the present application is prepared by using the ceramic coating material and the preparation method described above. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only illustrate the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings.

[0026] Figure 1 Typical microstructure schematic diagram of the thermal barrier coating prepared in Embodiment One of the present application;

[0027] Figure 2 Test results of the volume heat capacity and the thermal conductivity of the ceramic coating of the thermal barrier coating prepared in Embodiment One of the present application;

[0028] Figure 3 Top surface appearance schematic diagram of the piston coated with the thermal barrier coating prepared in Embodiment One of the present application;

[0029] Figure 4 Typical microstructure schematic diagram of the thermal barrier coating prepared in Embodiment Two of the present application;

[0030] Figure 5 Test results of the volume heat capacity and the thermal conductivity of the ceramic coating of the thermal barrier coating prepared in Embodiment Two of the present application;

[0031] Figure 6 Typical microstructure schematic diagram of the thermal barrier coating prepared in Embodiment Three of the present application;

[0032] Figure 7 Test results of the volume heat capacity and the thermal conductivity of the ceramic coating of the thermal barrier coating prepared in Embodiment Three of the present application. DETAILED DESCRIPTION

[0033] In order to make the above objectives, features and advantages of the present application more apparent and understandable, the specific embodiments of the present application will be described in detail below with reference to the drawings. It should be understood that the specific embodiments described here are only used to explain the present application, and are not used to limit the present application. DETAILED DESCRIPTION

[0034] The embodiment provides a diesel-powered piston surface ceramic coating material and a diesel-powered piston surface thermal barrier coating and a preparation method thereof, wherein the thermal barrier coating comprises a bonding layer and a ceramic coating, and the ceramic coating is prepared from the ceramic coating material provided by the embodiment.

[0035] It should be noted that in the embodiment, the "diesel-powered piston surface" mainly refers to the top surface of the piston. Of course, in other embodiments of the application, the surface can include other surfaces of the piston in addition to the top surface of the piston, for example, can also include the side surface of the piston, etc.

[0036] The diesel-powered piston surface ceramic coating material provided by the embodiment is a mixed and uniform plasma sprayed composite powder, which comprises 8YSZ powder, cordierite powder and silicon oxide powder. The 8YSZ powder is a hollow powder, and the hollow rate is 30-45%. The particle size of the cordierite powder is not greater than 30 μm, the content of the cordierite powder is 20-30 wt.%, the content of the silicon oxide powder is 5-8 wt.%, and the balance is 8YSZ powder. The chemical formula of 8YSZ is ZrO2-Y2O3, that is, 8 mol% yttria (Y2O3) stabilized zirconia (ZrO2), the doping amount of yttria is 8 mol%, and the balance is a zirconia matrix.

[0037] The diesel-powered piston surface ceramic coating material provided by the embodiment is a composite powder. The 8YSZ powder has high fracture toughness, and the high hollow rate of 30-45% enables the 8YSZ powder to form a well-bonded skeleton in the plasma spraying and melting deposition process, thereby improving the overall bonding force of the ceramic coating. The mineral raw material cordierite has the characteristics of low density, low specific heat capacity, low melting point and low thermal expansion coefficient, and has a high content, plays a role of partially melting deposition and partially semi-melting into the inside of the coating, and can reduce the density and volume heat capacity of each part as a whole. The melting point of silicon oxide is low, and the molten silicon oxide can play a role of enhancing the bonding force of the atmospheric plasma sprayed layer. At the same time, silicon oxide also has the characteristic of low density, which can reduce the overall density. After the 8YSZ powder, the cordierite powder and the silicon oxide powder are mixed uniformly at an optimized ratio, the ceramic coating material provided by the embodiment is obtained.

[0038] The ceramic coating obtained by spraying the above ceramic coating material through the atmospheric plasma spraying process has a porous and complex structure, the cordierite with low density and specific heat capacity is uniformly doped in the inside and distributed between the pores, so that the entire ceramic coating has low volume heat capacity and low thermal conductivity. In the working temperature range of 400-600 ℃ of the piston top, the thermal conductivity is lower than 0.6 W / m·K, and the volume heat capacity is lower than 2000 KJ / m 3·K. The ceramic coating also has a high bonding strength due to the effects of 8YSZ and silicon oxide, which can be greater than 30 MPa, thereby having a strong anti-peeling ability. In addition, the ceramic coating has a low density due to the high porosity of 8YSZ and the low densities of cordierite and silicon oxide. That is, the ceramic coating prepared from the diesel-powered piston surface ceramic coating material provided in the embodiment has the advantages of low bulk heat capacity, low thermal conductivity, low density, and high bonding strength, can meet the application requirements of high-performance coatings on the surface of diesel-powered pistons, can improve the thermal efficiency of diesel-powered engines and reduce engine fuel consumption, and has excellent service reliability.

[0039] Specifically, the impurity content of a single oxide in the 8YSZ powder is less than 100 ppm, and the hafnium oxide (HfO2) content is less than 2 wt.%. That is, the 8YSZ powder used in the embodiment is a high-purity hollow powder, which can fully utilize the toughness of the 8YSZ powder and effectively ensure the overall bonding strength of the ceramic coating prepared therefrom.

[0040] Specifically, the particle size of the 8YSZ powder ranges from 25 to 75 μm, and is a spherical powder prepared by an agglomeration sintering-plasma spheroidization process. The 8YSZ powder prepared in this way and the 8YSZ powder within this particle size range has good melting effect in the plasma, and the deposition efficiency can reach 40-50%.

[0041] Specifically, the cordierite powder is an irregularly shaped powder prepared by a crushing method, which has a simple process and low cost.

[0042] Specifically, the purity of the silicon oxide powder is greater than 99.5 wt.%. By using high-purity silicon oxide, the interlamination bonding force of the prepared ceramic coating can be effectively ensured, thereby improving the overall bonding strength and anti-peeling ability of the coating.

[0043] Specifically, the ceramic coating material is a composite powder uniformly mixed by a mechanical method. The mechanical mixing process is simple, low in cost, and can effectively avoid changes in the properties of the powders in the material.

[0044] The diesel-powered piston surface thermal barrier coating preparation method provided in the embodiment includes the following steps:

[0045] Preparation of the bonding layer: an MCrAlY metal bonding layer is prepared on the surface of the diesel-powered piston by a high-velocity oxy-fuel spraying process or an atmospheric plasma spraying process, and the thickness of the bonding layer ranges from 50 to 150 μm; wherein the MCrAlY includes one of NiCrAlY, NiCoCrAlY, CoNiCrAlY, and CoCrAlY.

[0046] Preparation of ceramic coating: using the ceramic coating material described above, atmospheric plasma spraying is performed on the adhesive layer, the flow rate of the primary gas argon is in the range of 27-33 slpm, the flow rate of the secondary gas hydrogen is in the range of 5-10 slpm, the spraying power of the spraying gun is in the range of 30-42 kW, the spraying distance is in the range of 80-100 mm, and the powder feeding amount is in the range of 20-40 g / min.

[0047] Of course, before the adhesive layer is prepared, the substrate also needs to be processed, and before the ceramic coating is prepared, processes such as drying the powder also need to be performed.

[0048] The diesel-powered piston surface thermal barrier coating provided in the embodiment is prepared using the ceramic coating material described above and the preparation method described above. Specifically, the thickness of the ceramic coating is in the range of 200-500 μm, that is, the thermal barrier coating provided in the embodiment has a relatively small thickness of the ceramic coating, and in combination with the advantages of low volumetric heat capacity and low thermal conductivity, it has less heat storage, responds to the environment temperature quickly, and is therefore suitable for use as a diesel-powered piston surface thermal barrier coating.

[0049] The diesel-powered piston surface ceramic coating material, thermal barrier coating, and preparation method thereof provided in the present application will be described in more detail below through three specific embodiments.

[0050] Embodiment One

[0051] A diesel-powered piston surface ceramic coating material, thermal barrier coating, and preparation method thereof, wherein the ceramic coating material is a composite spraying powder prepared by uniformly mixing three kinds of powders in a certain proportion, the high-purity, high-hollow-ratio 8YSZ powder: cordierite powder: silicon oxide powder = 72 wt. %: 20 wt. %: 8 wt. %, the three kinds of powders are accurately weighed and uniformly mechanically mixed in proportion, and then a ceramic coating is deposited on the surface of the adhesive layer by using an atmospheric plasma spraying process, thereby obtaining the final thermal barrier coating.

[0052] The specific steps are as follows:

[0053] S100, preparation of ceramic coating material

[0054] S110, preparation of component A, i.e., high-purity, high-hollow-ratio 8YSZ powder, the main impurity content of which is less than 100 ppm of single oxide, the hafnium oxide content is less than 2 wt. %, the powder is spherical powder, the particle size is in the range of 25-75 μm, the hollow ratio is 30-45 %, and the spraying deposition efficiency is 40-50 %; the qualified powder is ready for use;

[0055] S120, preparation of component B, i.e., cordierite powder, the particle size of which is -30 μm, and the powder is irregularly broken and formed;

[0056] S130, preparing component C, i.e. silicon oxide powder, purity greater than 99.5wt.%;

[0057] S140, using a mechanical method to fully mix A:B:C according to 72wt. %:20wt. %:8wt. %, and a coating plasma spraying powder for a piston top is formed.

[0058] S200, drying the powder

[0059] Before spraying, the powder is dried at 100℃±20℃ for 2h for plasma spraying.

[0060] S300, processing the substrate

[0061] A 24-mesh white corundum sand is used to sand blast the surface of the cast iron (or cast steel) substrate for roughening.

[0062] S400, preparing a bonding layer

[0063] A high-velocity oxygen-fuel (HVOF) is used to prepare a NiCrAlY metal bonding layer, and the bonding layer has a thickness of 80-120μm.

[0064] S500, preparing a ceramic coating

[0065] S510, clamping: using a high-temperature adhesive tape and a tool to protect the piston, and mounting the protected piston on a rotary table that can be controlled in linkage with a robot;

[0066] S520, setting a spraying trajectory: completing the optimization setting of the spraying trajectory according to the piston profile features; in this step, off-line programming can be used to determine the spraying angle, the rotary table speed and the spraying trajectory according to the piston profile features, and to compile the optimized spraying trajectory.

[0067] S530, preheating: using a 25kW atmospheric plasma to preheat the surface of the bonding layer to 200-240℃;

[0068] S540, ceramic coating spraying: the spraying gun power is 36kW, the plasma main gas Ar flow rate is 29-30slpm, the secondary gas H2 flow rate is 5-6slpm, the powder feeding amount is 32g / min, and the spraying distance is 90mm.

[0069] S550, post-processing: after the workpiece is cooled, a 2000-mesh white alumina sandpaper is used to polish the surface coating to a roughness of less than 3.2μm, so as to protect the surface profile and reduce the influence of the coating surface roughness on the flow field.

[0070] The performance of the prepared thermal barrier coating is evaluated and verified.

[0071] Figure 1 The microstructure of the thermal barrier coating prepared in this embodiment is shown in FIG. Figure 1 As shown, the ceramic coating has a uniform structure and is a composite structure of porous + second phase. The second phase, namely the cordierite phase, is uniformly dispersed in the ceramic coating.

[0072] from Figure 1 It can also be seen that the interface between the ceramic coating and the adhesive layer is well bonded. Table 1 shows the bonding strength test results of the ceramic coating of the thermal barrier coating prepared in this embodiment. The average bonding strength is as high as 39 MPa, indicating that the ceramic coating of the thermal barrier coating prepared in this embodiment has a relatively high bonding strength.

[0073] Figure 2 The test results of the volume heat capacity and thermal conductivity of the ceramic coating of the thermal barrier coating prepared in this embodiment are shown in FIG. Figure 2 As shown in the figure, in the range of 400-600℃, the volume heat capacity of the ceramic coating is less than 2000KJ / (m 3 ·K), thermal conductivity is less than 0.6W / (m·K), and both volume heat capacity and thermal conductivity are relatively low.

[0074] Figure 3 A piston having a thermal barrier coating prepared in this embodiment is shown. Figure 3 As shown in the figure, the thermal barrier coating completely and evenly covers the surface of the part without any leakage or overspray.

[0075] Table 1 Test results of bonding strength of ceramic coating in thermal barrier coating prepared in Example 1

[0076]

[0077] Example 2

[0078] A ceramic coating material and a thermal barrier coating for the surface of a diesel power piston and a preparation method thereof. The ceramic coating material is a composite spray powder obtained by uniformly mixing three different component powders in a certain proportion: high-purity, high-hollowness 8YSZ powder: cordierite powder: silicon oxide powder = 65wt.%, 30wt.%, and 5wt.%. The above three powders are accurately weighed in proportion and mechanically mixed uniformly, and then the ceramic coating is deposited on the surface of the bonding layer using an atmospheric plasma spraying process to obtain the final thermal barrier coating.

[0079] The specific steps are as follows:

[0080] S100, preparation of ceramic coating materials

[0081] S110, preparing component A, i.e. high-purity and high-hollow ratio 8YSZ powder, the main impurity content of single oxide is less than 100 ppm, the hafnium oxide content is less than 2 wt.%, the powder is spherical powder, the particle size range is 25-75 μm, the hollow ratio is 30-45%, and the spraying deposition efficiency reaches 40-50%; the qualified powder is standby;

[0082] S120, preparing component B, i.e. cordierite powder, the powder particle size range is -30 μm, and the powder is irregularly broken and formed;

[0083] S130, preparing component C, i.e. silicon oxide powder, the purity is greater than 99.5 wt.%;

[0084] S140, the A:B:C is fully mixed uniformly according to 65 wt.%:30 wt.%:5 wt.% by using a mechanical method, and the plasma spraying powder for the piston top coating is formed.

[0085] S200, drying the powder

[0086] The powder is dried at 100℃±20℃ for 2 h before spraying, and is used for plasma spraying.

[0087] S300, processing the substrate

[0088] The aluminum alloy substrate surface is sandblasted and roughened by using 60-mesh white corundum sand.

[0089] S400, preparing a bonding layer

[0090] The NiCrAlY metal bonding layer is prepared by using high-velocity oxygen fuel spraying (HVOF), and the bonding layer thickness is 80-120 μm.

[0091] S500, preparing a ceramic coating

[0092] S510, clamping: the high-temperature adhesive tape and tooling are used to protect the piston, and the protected piston is installed on a rotary table which can be controlled in linkage with a manipulator;

[0093] S520, setting a spraying track: the spraying track optimization setting is completed according to the piston profile characteristics; in this step, the off-line programming can be used to determine the spraying angle, rotary table speed and spraying track according to the piston profile characteristics, and the optimized spraying track is prepared;

[0094] S530, preheating: the bonding layer surface is preheated to 100-150℃ by using a 25 kW atmospheric plasma;

[0095] S540, ceramic coating spraying: the spraying gun power is 36 kW, the plasma main gas Ar flow rate is 27-29 slpm, the secondary gas H2 flow rate is 3-5 slpm, the powder feeding amount is 36 g / min, and the spraying distance is 100 mm;

[0096] S550, post-processing: After the workpiece cools down, use 2000 mesh white aluminum oxide sandpaper to polish the surface coating until the surface roughness of the coating is less than 3.2μm, to ensure the surface profile and reduce the influence of the coating surface roughness on the flow field.

[0097] This example also evaluates and verifies the performance of the prepared thermal barrier coating.

[0098] Figure 4 The microstructure of the thermal barrier coating prepared in this embodiment is shown in FIG. Figure 4 As shown, the ceramic coating has a uniform structure and is a composite structure of porous + second phase. The second phase, namely the cordierite phase, is uniformly dispersed in the ceramic coating.

[0099] from Figure 4 It can also be seen that the interface between the ceramic coating and the adhesive layer is well bonded. Table 2 shows the bonding strength test results of the ceramic coating of the thermal barrier coating prepared in this embodiment. The average bonding strength reaches over 30 MPa, indicating that the bonding strength of the ceramic coating of the thermal barrier coating prepared in this embodiment is also relatively high.

[0100] Figure 5 The test results of the volume heat capacity and thermal conductivity of the ceramic coating of the thermal barrier coating prepared in this embodiment are shown in FIG. Figure 5 As shown in the figure, in the range of 400-600℃, the volume heat capacity of the ceramic coating is less than 2000KJ / (m 3 ·K), thermal conductivity is less than 0.6W / (m·K), and both volume heat capacity and thermal conductivity are relatively low.

[0101] Table 2 Test results of bonding strength of ceramic coating in thermal barrier coating prepared in Example 2

[0102]

[0103] Example 3

[0104] A ceramic coating material and a thermal barrier coating for the surface of a diesel power piston and a preparation method thereof. The ceramic coating material is a composite spray powder obtained by uniformly mixing three different component powders in a certain proportion: high-purity, high-hollowness 8YSZ powder: cordierite powder: silicon oxide powder = 68wt.%, 25wt.%, and 7wt.%. The above three powders are accurately weighed in proportion and mechanically mixed uniformly, and then an atmospheric plasma spray process is used to deposit a ceramic coating on the surface of the bonding layer to obtain the final thermal barrier coating.

[0105] The specific steps are as follows:

[0106] S100, preparation of ceramic coating materials

[0107] S110, preparing component A, i.e. high-purity and high-hollow ratio 8YSZ powder, the content of main impurities in single oxide is less than 100 ppm, the content of hafnium oxide is less than 2 wt.%, the powder is spherical powder, the particle size range is 25-75 μm, the hollow ratio is 30-45%, and the spraying deposition efficiency is 40-50%; the qualified powder is standby;

[0108] S120, preparing component B, i.e. cordierite powder, the particle size range of the powder is -30 μm, and the powder is irregularly broken and formed;

[0109] S130, preparing component C, i.e. silicon oxide powder, the purity is greater than 99.5 wt.%;

[0110] S140, mechanically mixing A:B:C in the proportion of 68 wt. %:25 wt. %:7 wt. % to form a coating plasma spraying powder for piston top.

[0111] S200, drying the powder

[0112] The powder is dried at 100℃±20℃ for 2 h before spraying, and is used for plasma spraying.

[0113] S300, processing the substrate

[0114] The surface of the cast iron substrate is sandblasted and roughened by using 24-mesh white corundum sand.

[0115] S400, preparing a bonding layer

[0116] The NiCrAlY metal bonding layer is prepared by using high-velocity oxygen fuel (HVOF), and the thickness of the bonding layer is 80-120 μm.

[0117] S500, preparing a ceramic coating

[0118] S510, clamping: the piston is protected by using high-temperature adhesive tape and tooling, and the protected piston is installed on a rotary table which can be controlled in linkage with a robot;

[0119] S520, setting a spraying track: the spraying track is optimized and set according to the features of the piston profile; in this step, off-line programming can be used to determine the spraying angle, rotary table speed and spraying track according to the features of the piston profile, and the optimized spraying track is prepared;

[0120] S530, preheating: the surface of the bonding layer is preheated to 200-240℃ by using a 25 kW atmospheric plasma;

[0121] S540, ceramic coating spraying: the spraying gun power is 42 kW, the primary gas Ar flow rate is 29-30 slpm, the secondary gas H2 flow rate is 8-10 slpm, the powder feeding amount is 24 g / min, and the spraying distance is 80 mm;

[0122] S550, post-processing: after the workpiece is cooled, a 2000-mesh white alumina sandpaper is used to polish the surface coating, and the coating surface roughness is polished to be less than 3.2 μm, so as to ensure the surface profile and reduce the influence of the coating surface roughness on the flow field.

[0123] The performance of the prepared thermal barrier coating is also evaluated and verified in this embodiment.

[0124] Figure 6 The microstructure of the thermal barrier coating prepared in this embodiment is shown in FIG. 1. Figure 6 As shown in FIG. 1, the ceramic coating has a uniform structure, and the ceramic coating has a composite structure of pores + second phase, and the second phase, i.e., the cordierite phase, is uniformly and dispersedly distributed in the ceramic coating.

[0125] As shown in FIG. 2, the ceramic coating and the bonding layer are well combined. Figure 6 Table 3 shows the test results of the bonding strength of the ceramic coating of the thermal barrier coating prepared in this embodiment, and the average bonding strength is close to 35 MPa, which indicates that the bonding strength of the ceramic coating of the thermal barrier coating prepared in this embodiment is also relatively high.

[0126] Figure 7 The test results of the volume heat capacity and the thermal conductivity of the ceramic coating of the thermal barrier coating prepared in this embodiment are shown in FIG. 3. Figure 7 As shown in FIG. 3, in the range of 400-600℃, the volume heat capacity of the ceramic coating is less than 2000 KJ / (m 3 ·K), and the thermal conductivity is less than 0.6 W / (m·K), and both the volume heat capacity and the thermal conductivity are relatively low.

[0127] Table 3 shows the test results of the bonding strength of the ceramic coating of the thermal barrier coating prepared in this embodiment, and the average bonding strength is close to 35 MPa, which indicates that the bonding strength of the ceramic coating of the thermal barrier coating prepared in this embodiment is also relatively high.

[0128]

[0129] In summary, in this embodiment, the thin-shell high-hollow-ratio hollow powder 8YSZ with a high melting factor is used as the main body, the silicon oxide is used as the low-melting-point phase to increase the sheet layer adhesion, the cordierite is introduced as the second phase with low density and low thermal conductivity, and the new type of ceramic coating prepared by atmospheric plasma spraying fully gives play to the advantages of the main phase 8YSZ phase and the second phase cordierite phase, has high fracture toughness and good sheet layer adhesion, and the added silicon oxide phase can also inhibit microcracks, thereby reducing the microcrack density and improving the durability, i.e., low thermal conductivity, low volume heat capacity, low density, high porosity, high bonding strength, and high anti-peeling ability, which can meet the application requirements of the high-performance coating on the surface of the diesel-powered piston, can improve the thermal efficiency of the diesel-powered engine and reduce the oil consumption of the engine, and has excellent service reliability.

[0130] Finally, it should be noted that, in this document, the term "only" is used simply to set off from another element, and not to necessarily require or imply that only that element is present. Also, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0131] The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A ceramic coating material for the surface of a diesel power piston, characterized in that: The ceramic coating material is a uniformly mixed plasma sprayed composite powder, including 8YSZ powder, cordierite powder and silica powder. The 8YSZ powder is a hollow powder with a hollow rate of 30-45%; the particle size of the cordierite powder is not greater than 30 μm, the content of the cordierite powder is 20-30 wt.%, the content of the silica powder is 5-8 wt.%, and the balance is the 8YSZ powder.

2. The diesel power piston surface ceramic coating material according to claim 1, characterized in that: In the 8YSZ powder, the impurity content of a single oxide is less than 100 ppm, and the hafnium oxide content is less than 2 wt.%.

3. The diesel power piston surface ceramic coating material according to claim 2, characterized in that: The particle size range of the 8YSZ powder is 25 to 75 μm.

4. The diesel power piston surface ceramic coating material according to claim 3, characterized in that: The 8YSZ powder is a spherical powder prepared by agglomeration sintering-plasma spheroidization process.

5. The diesel power piston surface ceramic coating material according to claim 1, characterized in that: The cordierite powder is an irregularly shaped powder prepared by a crushing method.

6. The diesel power piston surface ceramic coating material according to claim 1, characterized in that: The purity of the silicon oxide powder is greater than 99.5 wt.%.

7. The diesel power piston surface ceramic coating material according to any one of claims 1 to 6, characterized in that: The ceramic coating material is a composite powder uniformly mixed by a mechanical method.

8. A method for preparing a thermal barrier coating on the surface of a diesel power piston, characterized in that: The thermal barrier coating comprises an adhesive layer and a ceramic coating, and the preparation method comprises the following steps: Preparation of bonding layer: using supersonic flame spraying process or atmospheric plasma spraying process to spray and prepare MCrAlY metal bonding layer on the surface of the diesel power piston, wherein the thickness of the bonding layer ranges from 50 to 150 μm; Preparation of ceramic coating: Using the ceramic coating material described in any one of claims 1-7, atmospheric plasma spraying is performed on the bonding layer, the flow range of the plasma main gas argon is 27-33slpm, the flow range of the secondary gas hydrogen is 5-10slpm, the spraying power range of the spray gun is 30-42kW, the spraying distance range is 80-100mm, and the powder feeding range is 20-40g / min.

9. A thermal barrier coating on the surface of a diesel power piston, characterized in that: The ceramic coating is prepared by using the ceramic coating material according to any one of claims 1 to 7 and the preparation method according to claim 8.

10. The thermal barrier coating on the surface of a diesel power piston according to claim 9, characterized in that: The thickness of the ceramic coating ranges from 200 to 500 μm.

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